The present invention relates to a method for the substantial removal of bacterial, plant, algal, or fungal components, such as endotoxin, from aqueous solutions by contact of the aqueous solution with a synthetic hydrated calcium silicate.
Throughout this application, various publications, patents and published patent applications are referred to by an identifying citation. Corresponding complete citations are provided below under the heading xe2x80x9cReferencesxe2x80x9d. The disclosures of the publications, patents and publications referenced in this application are hereby incorporated by reference herein in their entirety.
Endotoxin is a lipopolysaccharide (LPS)-protein complex that is a component of the outer membrane of Gram negative bacteria. The LPS portion of the complex can be further broken down into three distinct covalently linked domains: the O antigen polysaccharide side chain, the core oligosaccharides, and the lipid A. The lipid A portion of endotoxin is critical for most biological activity and is responsible for toxicity.
During the course of bacterial infection (i.e., sepsis), LPS is released from the surface of bacteria cells, interacts with a variety of host circulating blood plasma proteins (LPS-binding proteins), and then binds to specific LPS receptors on a variety of host cells (circulating blood cells or organ-specific endothelial cells). LPS induces the host cell production and release of a variety of potent, immunologically active cytokines and other mediators of the inflammatory response. Interleukin 1 (IL-1) and tumor necrosis factor (TNF) are two of the key cytokines generated by LPS-stimulated host cells. IL-1 and TNF promote the local and systemic inflammatory processes of a wide variety of cell types, which in turn produce the clinical features of sepsis that can include fever, hypotension, vasodilatation, and tissue necrosis/organ failure (septic shock). See Morrison et al., 1994 and Bone, 1991.
Endotoxin contamination is a major concern in the manufacturing of human and animal pharmaceutical preparations, medical device components, and pharmaceutical- and medical device-related processing aids (i.e. chromatography and filtration media storage solutions). Contaminated water is the principal source of endotoxin in these products.
Typical high purity water for injection (WFI) systems in place for the manufacture of a medically-related material include a number of system components, including distillation, reverse osmosis, filtration, and ozonation units. Downstream system components include storage tanks, circulating loops for final use, and point-of-use plumbing drops to individual manufacturing suites. System components, in particular downstream components, are subject to fouling and bacterial colonization. The colonization with water-borne Gram negative bacterial species such as the pseudomonads can become a constant source of bioburden and endotoxin. Live microorganisms or their breakdown products (e.g. endotoxin) can accumulate within pipes and at their inner surfaces, particularly near threaded connections, joints, elbows or dead legs. See Schaule et al., 1997 and Cooper et al., 1998.
Rigorous monitoring of a water system is required to ensure that endotoxin is not introduced into the aqueous solutions that are prepared for use in the manufacture of a pharmaceutical or medical device product. However, even with vigilant monitoring, aqueous solutions prepared from water with endotoxin levels that are below conventional detection limits can become problematic, as the processing solutions made from the water may be employed for production unit operations where large volumes are used in repeated-cycle concentration steps (e.g. chromatography, ultrafiltration) and where Gram negative bacteria or endotoxin may be retained.
Other sources of endotoxin introduced into the aqueous solutions used for the production of pharmaceutical or medical device products can be derived from bacterial or endotoxin contamination of the chemical or other commodity ingredients used to formulate a process solution.
Removal of endotoxin from aqueous based solutions can be difficult and time-consuming. Heat inactivation or ultrafiltration are highly effective, but cannot be used when the solution contains ingredients that are heat labile, such as enzymes, and carbohydrates, or macromolecular, such as large or polymeric proteins, respectively. See Sharma, 1986 and Sweadner et al., 1977. General ion exchange chromatography methods have been developed for removal of residual endotoxin contamination from aqueous-based solutions; however, their binding capacities are often low. See Sharma, 1986. Specific endotoxin affinity resin products have been developed (Acticlean Etox(copyright), Sterogene, Carlsbad, Calif.), and End-X(copyright), (Seikagaku America, Falmouth, Mass); however, in order to facilitate their economical use at commercial scale, they must typically be regenerated and cleaned-in-place for repeated use. See Adner et al., 1994. The cleaning and repeated-use procedures employed in federally-regulated industries such as pharmaceutical manufacturing are labor intensive and subject to time consuming validation studies required to document the potential for the generation of resin leachables and the anticipated resin useful life. See Seely et al., 1994.
Methods for the removal or separation of organic components from biological fluids, such as mammalian blood fluid, including whole blood, blood plasma, and blood serum have been described. See Belter et al., 1988, Harris, 1991, Kenney et al., 1992, Kent et al., 1996, Lydersen et al., 1994, and Walker, 1984.
Provided are methods for the substantial removal of organic substances, such as endotoxin, from aqueous solutions. The methods permit the preparation of aqueous solutions substantially depleted of organic substances, such as endotoxin. The methods permit the formation of aqueous solutions that are, for example, suitable for medical use.
In one embodiment, a method is provided for substantially removing at least one bacterial, plant, algal or fungal component from an aqueous solution comprising the component, the method comprising: contacting the aqueous solution with a synthetic hydrated calcium silicate (xe2x80x9cSHCSxe2x80x9d); and substantially removing the component from the aqueous solution. The method may include contacting the aqueous solution with a synthetic hydrated calcium silicate (SHCS) to permit the formation of a complex of the component and the SHCS; and separating the complex of the component and the SHCS from the aqueous solution, thereby to substantially remove the component from the aqueous solution. The complex is separated, for example, by centrifugation or sedimentation. During the contacting step, the pH of the aqueous solution can be, for example, maintained at about pH 5.5 to pH 9.5, or about pH 5.5 to pH 7.5.
The bacterial, plant, algal or fungal component is, for example, a lipid, a lipopolysaccharide, glucan or a lipoprotein. The invention advantageously provides methods for removing endotoxin and other Limulus amebocyte lysate-reactive materials.
Aqueous solutions that can be treated, include, for example, water, chemically buffered aqueous solutions, pharmaceutical solutions, aqueous solutions comrising a nutritional supplement, culture media, and growth media. The aqueous solution can comprise, for example, pharmaceutical compendial water or non-compendial water.
The SHCS, for example, may be crystalline. In one embodiment, the method of removal comprises passing the aqueous solution through the SHCS supported on a septum, thereby to contact the aqueous solution with a SHCS to permit the formation of a complex of the organic substance and the SHCS, and thereby to separate the complex of the organic substance and-the SHCS from the aqueous solution. In another embodiment, the method comprises passing the aqueous solution through a holding device comprising the SHCS, thereby to contact the aqueous solution with the SHCS to permit the formation of a complex of the organic substance and the SHCS, and thereby to separate the complex of the organic substance and the SHCS from the aqueous solution. The holding device is, for example, a cartridge, filter pad, sheet, or membrane.